1. Field of the Invention
The present invention relates to apparatus and a related method for reducing disabling glare and driver fatigue due to artificial or natural light-impinging on an occupant of a vehicle by effecting controlled influence on pupil size of the driver or other occupants.
2. Description of the Prior Art
An important aspect of safety and comfort of vehicle occupants is avoidance or minimizing of glare such as glare created at night due to sources of light external or internal of the vehicle. In the case of a road vehicle, such as an automobile, truck or van, for example, oncoming headlights, street lights, lights projected from the rear of the vehicle through vehicle rear view mirrors and other sources of light can cause a driver to have visual discomfort. Such fluctuations in visual acuity can result in vehicular accidents, and even if no such accidents occur, the stress of such exposure to glare can create fatigue.
Glare generally results from two sources. The first is the scatter effect of the peripheral portions of the human lens. The naturally dilated pupil changes the refractive properties of the eye. The larger the pupil opening, the more the influence the peripheral portions of the lens will have on the focusing of light rays. The peripheral portions of the lens bend the light rays differently than the nodal rays or the central rays of light. This is called night myopia. This peripheral influence results in more poorly focused rays of light which, in turn, produce a more poorly focused image. During night driving, for example, under normal circumstances, the driver's and occupant's pupils have relatively large openings to compensate for the low level of ambient light. A second effect of large pupil opening is the increase of glare as a result of the total amount of light entering the eye. The larger the pupil opening, the more light that enters the eye. As a result, the peripheral entry of light and the larger intensity of light combine to produce a poorly focused image which is generally referred to as "glare."
It has previously been suggested to employ a film over a portion of the windows of vehicles in order to minimize night glare. One of the problems with such an approach is that in excluding light to minimize glare, it also excludes light which might contribute, under certain conditions, to better vision and enhanced safety.
It has also been suggested to place a light bulb at the extreme left of the windshield so as to cause light to impinge on the eyes of the driver and the inner surface of the windshield. See U.S. Pat. No. 2,484,796. This disclosure, which also suggests the influence of color in this context, would provide primary focus on the windshield interior and would not appear to provide equal light intensity to both of the driver's eyes. It also does not disclose an elongated light source extending along the windshield.
U.S. Pat. No. 3,630,567 discloses an internal single bulb device which is said to minimize glare. It causes light to impinge on the inside of the windshield. It also provides means for controlling the intensity of the light.
U.S. Pat. No. 2,277,784 also discloses a single light source positioned to the extreme left of the windshield. The light source, which may be colored, is said to be controlled by a floor-mounted switch.
U.S. Pat. No. 1,929,298 also discloses a single bulb positioned at the left-hand side of the windshield for resisting headlight glare during night driving. A rheostat is provided to adjust the intensity of the light.
In spite of the foregoing prior art teachings, there remains a very real and substantial need for apparatus and an associated method which will effectively resist undesired glare, particularly during night driving.